#include<iostream>
#include<unistd.h>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<sys/types.h>
#include<sys/wait.h>
#include<pwd.h>
#include <limits.h>
using namespace std;


#define COMMAND_SIZE 1024
#define FORMAT "%s@%s:%s$ "

//下面是shell的全局数据

#define MAXARGC 128
char* g_argv[MAXARGC];
int g_argc = 0;

const char *GetUserName()
{
	const char *name = getenv("USER");
	return name == NULL ? "None" : name;
}

const char *GetHostName()
{
	const char *hostname = getenv("HOSTNAME");
	return  hostname == NULL ? "None" : hostname;
}

const char *GetPwd()
{
	const char *pwd = getenv("PWD");
	return pwd == NULL ? "None" : pwd;
}

// /  /a/b/c
std::string DirName(const char *pwd)
{
#define SLASH "/"
	const char *home_1 = getenv("HOME");
	std::string home = home_1;
	std::string dir = pwd;
	auto pos = dir.find(home);
	if(pos == std::string::npos) return "BUG?";
	return "~/"+dir.substr(home.size()+1);
}

void MakeCommandLine(char Cmd_prompt[],int size)
{
	//snprintf(Cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),DirName(GetPwd()).c_str());
	snprintf(Cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),GetPwd());
}

void PrintCommandPrompt()
{
	char prompt[COMMAND_SIZE];
	MakeCommandLine(prompt,COMMAND_SIZE);
	printf("%s",prompt);
	fflush(stdout);
}

bool GetCommandLine(char *out,int size)
{
	//ls -l -a => 字符串
	char *c = fgets(out,size,stdin);
	if(c == NULL) return false;
	out[strlen(out)-1] = 0;//清理回车\n
	if(strlen(out) == 0) return false;
	return true;
}

//3.命令行分析"ls -a -l"  -> ls    -a     -l
bool CommandParse(char *commandline)
{
#define SEP " "
	g_argc = 0;
	//命令行分析"ls -a -l"  -> ls    -a     -l
	g_argv[g_argc++] =strtok(commandline,SEP);
	
	while(g_argv[g_argc++] = strtok(nullptr,SEP));
	g_argc--;
	return true;
}

void PrintArgv()
{
	for(int i=0;g_argv[i];i++)
	{
		printf("argv[%d]->%s\n",i,g_argv[i]);
	}
	printf("%d\n",g_argc);
}

int Execute()
{
		//4.执行命令
		pid_t id = fork();
		if(id == 0)
		{
			//child
			execvp(g_argv[0],g_argv);
			exit(1);
		}
		pid_t rid = waitpid(id,nullptr,0);
		//void(rid);//rid使用一下
		return 0;
}

int main()
{
	while(true)
	{
		
		//1.输出命令行提示符
		PrintCommandPrompt();

		//2.获取用户输入的命令
		char commandline[COMMAND_SIZE];
		if(!GetCommandLine(commandline,sizeof(commandline)))
			continue;
		
		printf("echo %s\n",commandline);
		//3.命令行分析"ls -a -l"  -> ls    -a     -l
		CommandParse(commandline);

		//PrintArgv();i
		
		//4.
		Execute();
	}	
	return 0;
}
